粤西残斑岩的锆石U-Pb年龄及其地质意义

粤西残斑岩脉是由花岗斑岩脉遭受后期地质作用改造而成的 ,具有片状构造 ,片理产状与地层围岩一致。通过对该残斑岩的颗粒锆石U -Pb年龄测定 ,莸得两条不一致线 ,它们的下交点年龄分别为 40 4±6Ma和 42 8± 17Ma ,从而确定残斑岩脉的侵入年龄为 40 4～ 42 8Ma ,属加里东期。根据上交点年龄和2 0 7Pb/2 0 6Pb年龄推断 ,其源区物质较复杂 ,包含有 1737Ma、2 16 5Ma和 2 494Ma的物质 ,暗示粤西云开隆起区存在中、古元古代以及太古宙基底。

ZIRCON U-Pb AGES AND THEIR GEOLOGIC IMPLICATION OF PORPHYROID IN THE WEST OF GUANGDONG PROVINCE

Porphyroid dikes in the west of Guangdong Province were derived from transformed granite\|porphyries. Zircon U\|Pb ages have been determined from the porphyroid. In two U\|Pb concordia diagrams are defined two lower intercept ages of 404±6Ma and 428±17Ma and two upper intercept ages of 1737±27Ma and 2165±5Ma. Besides, the eighth sample has a \{\}\+\{207\}Pb/\+\{206\}Pb age of 2494±2Ma. From the above we come to the conclusion that the age of porphyroid diagenesis is 404～428 Ma, belonging to the Caledonian. Its source region materials include three portions whose ages are 1737 Ma, 2165 Ma and 2494 Ma, respectively. There are three kinds of basement rocks in the west of Guangdong Province: Middle Proterozoic, Lower Proterozoic and Archeozoic.